linux-kernel - Re: [RFC PATCH] RDMA/srp: Fix use-after-free in srp_exit_cmd

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Message-ID: <0d6ffcec-285a-37f8-5f2f-6a16e3631b92@acm.org>
Date:   Fri, 24 Jun 2022 16:57:47 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     Li Zhijian <lizhijian@...itsu.com>,
        Leon Romanovsky <leon@...nel.org>, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] RDMA/srp: Fix use-after-free in srp_exit_cmd_priv

On 6/24/22 16:47, Jason Gunthorpe wrote:
> On Fri, Jun 24, 2022 at 04:26:06PM -0700, Bart Van Assche wrote:
>> On 6/24/22 15:59, Jason Gunthorpe wrote:
>>> I don't even understand how get_device() prevents this call chain??
>>>
>>> It looks to me like the problem is srp_remove_one() is not waiting for
>>> or canceling some outstanding work.
>>
>> Hi Jason,
>>
>> My conclusions from the call traces in Li's email are as follows:
>> * scsi_host_dev_release() can get called after srp_remove_one().
>> * srp_exit_cmd_priv() uses the ib_device pointer. If srp_remove_one() is
>> called before srp_exit_cmd_priv() then a use-after-free is triggered.
> 
> Shouldn't srp_remove_one() wait for the scsi_host_dev to complete
> destruction? Clearly it cannot continue to exist once the IB device
> has been removed

That sounds like an interesting approach to me. Li, do you perhaps want 
to implement this approach?

Thanks,

Bart.